DCS is the English abbreviation of Distributed Control System (Distributed Control System), which is also called distributed control system in the domestic automatic control industry.
The so-called distributed control system, or distributed system in some materials, is a new type of computer control system compared to the centralized control system. Developed and evolved on the basis of. In terms of system functions, there is not much difference between DCS and centralized control systems, but they are completely different in the implementation methods of system functions.
First, the skeleton of DCS - the system network, which is the foundation and core of DCS. Since the network plays a decisive role in the real-time, reliability and scalability of the entire DCS system, each manufacturer has carefully designed it in this regard. For the DCS system network, it must meet the real-time requirements, that is, complete the transmission of information within a certain time limit. The "determined" time limit mentioned here means that information transmission can be completed within this time limit under any circumstances, and this time limit is determined based on the real-time requirements of the controlled process. Therefore, the indicator to measure the performance of the system network is not the speed of the network, commonly known as bits per second (bps), but the real-time nature of the system network, that is, how long it takes to ensure the completion of the transmission of the required information. . The system network must also be very reliable, and network communication cannot be interrupted under any circumstances. Therefore, most manufacturers' DCS adopt a dual bus, ring or dual star network topology. In order to meet the system scalability requirements, the maximum number of nodes that can be accessed on the system network should be several times larger than the actual number of nodes used. In this way, on the one hand, new nodes can be added at any time, and on the other hand, the system network can be operated with a lighter communication load to ensure the real-time performance and reliability of the system. During the actual operation of the system, each node's access to and from the network may occur at any time, especially the operator station. In this way, network reconstruction will be carried out frequently, and this operation must not affect the normal operation of the system. Therefore, the system The network should have strong online network reconstruction capabilities.
Secondly, this is a network node that completely handles on-site I/O and implements direct digital control (DOS) functions. Generally, an on-site I/O control station is set up in a set of DCS to share the I/O and control functions of the entire system. This can not only avoid the failure of the entire system due to the failure of one site, improve system reliability, but also enable each site to share data collection and control functions, which is beneficial to improving the performance of the entire system. The DCS operator station is a network node that handles all human-machine interface (HMI-Human Machine Interface or operator interface) functions related to running operations.
The system network is the engineering station of DCS. It is a network node for offline configuration, configuration work and online system supervision, control and maintenance of DCS. Its main function is to provide configuration of DCS. , configure the tool software (i.e. configuration software), and monitor the operation of each node on the DCS network in real time when the DCS is running online, so that the system engineer can adjust the system configuration and the settings of some system parameters in a timely manner through the engineering station. Keep DCS in the best working condition at all times. Different from centralized control systems, all DCS require system configuration function. It can be said that a system without system configuration function cannot be called DCS.
Since its advent in 1975, DCS has experienced more than 20 years of development. In the past twenty years, although DCS has not undergone major changes in the system architecture, its functions and performance have been greatly improved through continuous development and improvement. In general, DCS is developing in a more open, standardized, and productized direction.
As a computer control system in the field of production process automation, traditional DCS is only a narrow concept. If you think that DCS is just an automation system for the production process, it will lead to the wrong conclusion, because the meaning of the current computer control system has been greatly expanded. It not only includes various contents included in the DCS in the past, but also goes deeper into Every measuring equipment and actuator on site has been developed into all aspects of production management and business operations.
In the traditional sense, DCS now only refers to the automation of the production process control part, while the concept of industrial automation systems should be positioned at the level of comprehensive solutions for enterprises, that is, total solutions. Only by raising and solving problems from this perspective can computer automation truly play its due role.
DCS, the abbreviation of Distributed Control System, is generally called distributed control system in China. DCS is a multi-level computer system composed of process control level and process monitoring level and linked by communication network. It integrates 4C technologies such as computer, communication, display and control. Its basic idea is decentralized control, centralized operation, hierarchical management, Flexible configuration and easy configuration. DCS has the following characteristics:
(1) High reliability. Since DCS distributes system control functions on each computer, and the system structure adopts a fault-tolerant design, the failure of one computer will not cause the loss of other functions of the system. In addition, since each computer in the system has a relatively single task, special computers with specific structures and software can be used for the functions that need to be implemented, thereby improving the reliability of each computer in the system.
(2) Openness. DCS adopts an open, standardized, modular and serialized design. Each computer in the system uses LAN to communicate to realize information transmission. When the system functions need to be changed or expanded, new computers can be easily connected to the system communication network or Removing it from the network will hardly affect the work of other computers in the system.
Definition of DCS
DCS is the English abbreviation of Distributed Control System (Distributed Control System), which is also called distributed control system in the domestic automatic control industry.
It is a multi-level computer system composed of process control level and process monitoring level and linked by communication network. It integrates computer (Computer), communication (Communication), display (CRT) and control ( Control) and other 4C technologies, the basic ideas are decentralized control, centralized operation, hierarchical management, flexible configuration, and convenient configuration. )
After entering the 1990s, computer technology has advanced by leaps and bounds, and more new technologies have been applied to DCS. PLC is an electronic device developed for sequential logic control. It is mainly used to replace inflexible and bulky relay logic. Fieldbus technology has developed so rapidly since the mid-1990s that some people have made predictions: FCS based on fieldbus will replace DCS as the protagonist of the control system.
DCS is the abbreviation of Data Communication Subsystem.
Taking the rail transit industry as an example, DCS is a purely transparent and non-safety system. It is the carrier for sending messages between the control center and the train.
The second meaning of DCS: Dorsal Column Stimulator [Medical] Spinal Stimulator
In special control fields, such as nuclear power plant control systems, DCS means digital control system. ).
Major domestic DCS manufacturers include: Zhejiang University SUPCON, Hollysys (Beijing, Hangzhou), and Shanghai Xinhua. Foreign companies include Yokogawa, Honeywell, FOXBORO, Yamatake-Honeywell, and FISHER-ROSEMOUNT.
Overview of DCS characteristics and development
DCS is a decentralized The abbreviation of Distributed Control System is generally called distributed control system in China. It is a multi-level computer system composed of process control level and process monitoring level and linked by communication network. It integrates 4C technologies such as computer (Computer), communication (Communication), display (CRT) and control (Control). The basic idea is decentralized control, centralized operation, hierarchical management, flexible configuration, and convenient configuration.
DCS has the following characteristics:
(1) High reliability. Because DCS distributes system control functions on various computers, and the system structure adopts fault-tolerant design, a certain computer Failures that occur will not result in the loss of other functions of the system. In addition, since each computer in the system has a relatively single task, special computers with specific structures and software can be used for the functions that need to be implemented, thereby improving the reliability of each computer in the system.
(2) Open DCS adopts open, standardized, modular and serialized design. Each computer in the system uses LAN to communicate and realize information transmission. When the system functions need to be changed or expanded, they can New computers can be easily connected to or removed from the system communication network without affecting the work of other computers in the system.
(3) Flexibility: Configure software and hardware according to different process application objects through configuration software, that is, determine measurement and control signals and their connection relationships, select applicable control rules from the control algorithm library, and Basic graphics are called from the graphics library to form various monitoring and alarm screens required, thereby conveniently constructing the required control system.
(4) Easy to maintain small or micro special-purpose computers with single functions, which have the characteristics of simple and convenient maintenance. When a certain part or a certain computer fails, it can be maintained without affecting the operation of the entire system. Replace online and troubleshoot quickly.
(5) Coordination: Various data are transmitted between workstations through the communication network, and the entire system information is shared and coordinated to complete the overall function and optimization of the control system.
(6) The control functions are complete and the control algorithms are rich. It integrates continuous control, sequential control and batch control, and can realize advanced control such as cascade, feedforward, decoupling, adaptive and predictive control. And the required special control algorithms can be easily added. The structure of DCS is very flexible. It can be composed of dedicated management computer station, operator station, engineer station, recording station, field control station and data acquisition station, etc. It can also be composed of general-purpose servers, industrial control computers and programmable controllers. The process control level at the bottom generally implements data collection and control on-site through distributed on-site control stations, data acquisition stations, etc., and transmits it to the production monitoring level computer through the data communication network. The production monitoring level performs centralized operation and management of data from the process control level, such as various optimization calculations, statistical reports, fault diagnosis, display alarms, etc. With the development of computer technology, DCS can be connected to higher-performance computer equipment through the network as needed to achieve more advanced centralized management functions, such as planning and scheduling, warehousing management, energy management, etc.
The development and application status of DCS at home and abroad
In 1975, Honeywell, the largest instrument control company in the United States, launched its integrated distributed control system TDC-2000 (Toal D) to the world for the first time. ist ribu ted Con t ro l -2000), the publication of this system immediately aroused high praise from the American industrial control community, calling it "the most inspiring event". Major companies around the world have also followed suit and launched one distributed system after another. From then on, process control entered a new era of distributed systems.
During this period, there were CEN TUM launched by Yokogawa Company of Japan, MO S? of Taylor Instruments Company of the United States, DC?-400 of Fisher Company, N-90 of Bailey Company, Foxboro The company's Cpect rum and Germany's Siemens Telepermm.
With the rapid development of computers, especially microcomputers and network technology, and the fierce competition among manufacturers, DCS quickly developed from the first generation in the 1970s to the third generation in the early 1990s. DCS. Although the technical level of the distributed systems before this was already very high, there was one major drawback: dozens of models of systems launched by major companies were almost all patented products of the company. To protect their own interests, they use patent networks, which brings problems to the management of the entire factory and the entire enterprise.
With the development of computers and network development, various control manufacturers have adopted more commercial computer technology. In the late 1980s, many companies launched a new generation of distributed systems. The main feature is the use of local networks in the new systems. MAP protocol; citing intelligent transmitters and fieldbus structures; introducing PLC sequence control and batch control into the control software, so that DCS also has the functions of PLC.
By the early 1990s, the well-known DCSs in various countries were: 3000, Bailey's INFI-90, Rosemount's RS-3, West Hoose's WDPF, and Leeds & Nonthrup's MAX-1000. , I?A S of Foxbo ro, CEN TUM of Yokogawa, Japan. The ones mentioned here are all large-scale DCS. In order to meet the needs of the market, various manufacturers have also developed many small and medium-sized DCS systems such as S-9000, MAX-2, LXL, A2 PACS, etc.